Reactor and method for the treatment of particulate matter by electrical discharge

ABSTRACT

A reactor and method for the treatment of matter by plasma action. A plurality of electrode structures are positioned to define a reaction zone associated with the inter-electrode space. The inter-electrode space is conditioned (as by preionizing) and a series of discrete electrical discharges are produced throughout the reaction zone. In a preferred embodiment, the reaction zone is subjected to a sequence of discrete electrical discharges in a time interval less than the residence time of material to be treated within the reaction zone.

BACKGROUND OF THE INVENTION

The present invention relates generally to the treatment of matter byinteraction with plasma and, in particular, to a reactor and method foreffecting such treatment via discrete electrical discharges.

The relatively high energy levels available from plasma have recognizedvalue in the processing of many particulate materials. Typical knownmethods of generating plasma have relied on the conversion of electriccurrent into high temperature effluents of one kind or another which, byvirtue of their high temperature and enthalpy, interact with thefeedstocks, bringing about a higher rate of reaction than would takeplace at a low temperature. Most conventional methods of producing lowtemperature plasma, plasma torches ("plasmatrons"), for example, havenot proven industrially useful for the treatment of tonnage quantitiesof particulate matter, in themselves.

The difficulties encountered in the treatment of particulate materialswith low temperature plasmas are discussed in U.S. Pat. No. 4,361,441issued Nov. 30, 1982 in the name of Jozef K. Tylko, the co-inventorherein, which patent is hereby incorporated by reference. The expression"low temperature plasma" as defined in the incorporated patent is anarbitrary reference to plasmas having an ion temperature below 100,000°K. That convention is retained herein. Further, the term "particulatematter," as used herein, includes solid particles as well as fluids(gases or liquids), and combinations or mixtures thereof.

As described in the incorporated patent, the industrial application oflow temperature plasma technology has developed along two differentroutes. The first route (in which the volume of the arc discharge wasnot used for entrainment of feed stocks) chiefly utilized the point ofimpingement of the arc at the anode and behaved in this respect verymuch like electric arc furnaces. The second route, more relevant to thepresent invention, aims at the treatment of particles in the wholevolume of the plasma produced--treatment "in flight." For this purpose,it was required to expand the plasma and this involves increasing itsoriginal volume. This is the development of Jozef K. Tylko, one of theco-inventors herein.

Two distinct methods for plasma expansion are discussed in theincorporated patent. It should be noted that both of these methodsinvolve the establishment and maintenance of an expanded plasma volume.The more relevant of these methods to an understanding of the presentinvention is initially disclosed in British Patent Nos. 1,390,351-3. Inthis method, a plasma torch acting as a cathode was made to orbit in acircular path and at a small angle with the vertical, projecting the arcto a downstream annular electrode. A truncated conical plasma region wasdefined by the orbiting arc discharge. This method served well as alaboratory plasma furnace for studying many reactions. However,mechanical limitations resulting from the need to orbit the torchseverely limited the industrial utility of this method.

The method of the incorporated patent addressed many of the limitationsof the orbiting torch technology discussed above. In this methodology,an arc discharge was generated between stationary electrode structures,at least one of those structures being annular. As indicated in theincorporated patent, a primary requirement of the system was theestablishment and maintenance of an expanded plasma within the reactionzone between the electrode structures. Early versions of the methodologyof the incorporated patent also required utilization of a plasmatron.Later versions utilized a simple electrode structure as the centralcathode while maintaining an annular ring structure for the anode, theannular anode being formed by multiple anode segments. Such a system isdiscussed in a thesis prepared by Steven Anthony Vrchota in partialfulfillment of the requirements of a degree of Masters of Science at theUniversity of Minnesota dated April, 1991 and entitled Use of theSustained Shock Wave Reactor for the Recovery of Metals From ElectricArc Furnace Dust.

The method of the incorporated patent allowed a heavier loading ofmatter to be treated while taking advantage of an apparently anomalousbehavior of at least some matter in such plasmas. It was concluded thatthe presence of a dense suspension of particles in the plasma zoneincreased the effective energy flux causing rapid plasma-solidinteractions. It was noted that these interactions need not be purelythermal and, indeed, that the method of the incorporated patent utilizedthese non-thermal (anomalous) phenomena.

As indicated above, the difficulty in these prior art methods ismaintenance of the plasma-forming arc discharge. Generally, as thequantity of matter introduced into the expanded plasma increased, thelikelihood of extinction of the arc increased. Extinction of the arcstops the processing, with many attendant problems. This difficulty wasaddressed in the incorporated patent by the utilization of a rapidlyfluctuating potential difference between the cathode and the anodeelectrode structures while that discharge was circulating about theperiphery of the annular electrode structure (anode). However,maintaining the plasma at industrially significant feedstock loadingremained a problem. A pattern of least energy configuration would beestablished. Also, significant loading volumes remained a problem inthemselves, in that not all particles were treated.

In summary, the method of the incorporated patent resolved themechanical limitations in the prior art by orbiting the arc bynon-mechanical means whereby rapid rates of "rotation" far greater thanthose possible by mechanical means were attained. Additionally,pulsation of the arc by rapid changes in the applied power establishedconditions which improved the ability to maintain the arc dischargewhile also utilizing non-thermal phenomena which enhance the plasmaaction on the matter being treated. However, the perceived need tomaintain the arc discharge orbiting around the annular electrodestructure significantly limited the industrial utility of the method.Also, significant loading volumes remained a problem. During operation,a pattern of least energy configuration was established. As a result,particles were not uniformly treated.

SUMMARY OF THE INVENTION

The present invention provides the advantages of the method of theincorporated patent while dispensing with the need to maintain anorbiting arc discharge. Instead, a series of discrete electricaldischarges are utilized in a treatment or reaction zone defined byspaced electrode structures, the treatment zone containing large amountsof particles to be treated and the discharges acting on these particles"in flight." As described herein, these discharges may be sequential intime, but need not be sequential in space and may overlap in time andspace and may be simultaneous. Thus, the criticality of maintaining asequential orbiting discharge is eliminated.

As noted in the incorporated patent, the presence of a dense suspensionof particles in the treatment zone increases the effective energy fluxwhile utilizing non-thermal phenomena first recognized in the method ofthe incorporated patent. In particular, it is believed that thesenon-thermal phenomena are the result of the formation of "microfields"in which very high local potential differences and other associatedfluctuating anomalies occur. These high local potential differences andassociated anomalies appear to have a pronounced effect on the particlesbeing treated, such as the imposition of electrical and mechanicalstresses, assisting disruption and causing polarization, increasedionization, and interaction with solid state effects. Effects of thischaracter are essentially primarily non-thermal and reside in themicroscopic mechanisms of plasmas. As noted in the incorporated patent,they have been observed but have hitherto been dependent upon theestablishment and maintenance of a sufficiently stable plasma for theireconomic utilization.

It is recognized that the model presented herein is highly simplifiedbut does describe the basic mechanism which is believed to be operatingwithin the present invention while pointing out the primary distinctionbetween the present invention and the prior art--the necessity in theprior art of establishing and maintaining a stable expanded plasma. In abasic preferred embodiment in accordance with the present invention, areactor is provided having spaced electrode structures defining atreatment zone. The treatment zone is preionized in any desired mannerand discrete electrical discharges are produced throughout the treatmentzone. The discrete electrical discharges are produced in a desiredsequence and in a time interval less than, and preferably considerablyless than, the transit time of the matter to be treated through thetreatment zone. In a particularly preferred embodiment, and with anygiven electrode configuration, one or more of the electrode structuresmay alternatively function as anode or cathode. That is, the electrodestructures, in accordance with the present invention may operate with avariable polarity. While this variable polarity, in itself, is animportant feature of the present invention, it also highlights anessential difference between the present invention and the prior art.That is, an electrode utilized in the described prior art devices forthe establishment and maintenance of an expanded plasma within theinter-electrode space must maintain its polarity for maintenance of theexpanded plasma.

In addition to a reactor, the present invention provides a method forthe treatment of matter by electrical discharge including the steps ofpositioning the plurality of electrode structures to define a desiredinter-electrode space or spaces, conditioning the inter-electrode spaceas by preionizing that space in any desired manner, introducingparticulate matter to be treated to the inter-electrode space andproducing a plurality of discrete electrical discharges in a desiredsequence between said electrode structures. In accordance with thismethod, substantially the entire inter-electrode space is subjected todiscrete electrical discharges within a time interval less than theexpected residence time of a particle to be treated within theinter-electrode space.

In a specific preferred embodiment, a conical treatment zone isestablished by a central cathode and a plurality of circularly disposedanodes longitudinally displaced from the central cathode. Whilesuperficially similar to the disclosed embodiment in the incorporatedpatent, the structure may be differentiated. In particular, an arcdischarge need not "orbit" about an annular anode electrode structure.Instead, in accordance with the present invention, a series of discreteelectric discharges may sequentially move along circularly disposedanode structures. Additionally, any or all of such circularly disposedelectrode structures may function as a cathode--clearly differentiatingthe present invention from that of the incorporated patent.

Any number of distinct electrode configurations may be employed inaccordance with the particular application. Further, it is contemplatedthat the present invention may be utilized in the disposal of wastes(solid, liquid, or gaseous, or combinations thereof) in the productionof glasses or in the synthesis of compounds or other chemical orphysical reactions. The reactor may be operated over a wide range ofpressures (from below to above atmospheric pressure) and over a varietyof regimes (reducing, oxidizing or neutral).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view of a reactor according to thepresent invention;

FIG. 2 is a schematic illustration of a preferred electrodeconfiguration in accordance with the present invention and theircontrol;

FIG. 3 is a schematic diagram showing a preferred control circuit inaccordance with the present invention;

FIG. 4 is a schematic diagram illustrating a modification to a portionof the circuit of FIG. 3;

FIGS. 5A-5F are schematic diagrams illustrating a sequence of discreteelectrical discharges throughout a treatment zone defined by spacedelectrode structures;

FIG. 6 is a table showing the on/off states of the power switches ofFIG. 3 during part of an operating sequence.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagrammatic illustration of a reactor in accordance withthe present invention which incorporates many elements know to the priorart and which may be utilized in the practice of the invention herein.In the reactor of FIG. 1, feedstock dispensers 10 are connected throughelectrostatic charging probes 11 to a modular head 12 which alsoreceives gas for forming a plasma, coolant, and electrical supplies forthe start-up electrode. Downstream of the plasma head 12 is a reactionchamber 13 and electrode assembly section 14. The remaining portions ofthe reactor FIG. 1 are application specific and are utilized, forexample, if the reactor is to be used for energy recovery and include acombustion chamber 15 immediately below the electrode section 14 towhich controlled quantities of air are injected, at 16, for example, tocause combustion of carbon value separated in the reactor chamber 13. Aside duct 17 carries the resulting hot gases away for steam raising andelectricity generation while the solid residues pass through a coolingchamber 18 to a collector 19.

The reactor illustrated in FIG. 1 is, in the general terms described,similar to that illustrated in FIG. 3 of the incorporated patent and hasthe same breadth of application as described in the incorporated patent.

Referring now to FIG. 2, there is shown an axial electrode structure 20as may be contained in the modular head 12 of the reactor of FIG. 1 anda plurality of electrode structures 21-26 which may be circularlyarranged about the longitudinal center axis of the electrode assemblysection 14 of the reactor of FIG. 1. In the illustrated embodiment ofFIG. 2, there are six electrode structures 21-26 which, in accordancewith the present invention, may be simple rod shaped structures,graphitic or metallic, for example, to which a series of pulse chargesare applied as described hereinafter. Similarly, in accordance with thepresent invention, the electrode 20 may be a simple rod structuresimilar to the electrodes 21-26. Each of the electrodes 20-26 isconnected to a base current source 27 and a pulse current source 28 byassociated switches 30 controlled via Switch Control 29. Preferredimplementations of the switches 30 are discussed below with reference toFIGS. 3 and 4 and include control terminals, (represented by theterminal(s) 31 in FIG. 2) by which the potentials developed by basecurrent source 27 and pulse current source 28 may be selectively appliedbetween two or more of the electrodes 20-26, as described more fullybelow. The terminal(s) 31 may represent one or more control terminals asneeded by a particular implementation. This is represented herein by thedesignation "terminal(s)". Terminal(s) 31 of Switch Control 29 areconnected to the terminal(s) 31 associated with switches 30. Thoseconnections are not shown for the sake of clarity but are within theskill of one ordinarily skilled in the art.

As described above, the central electrode 20 of FIG. 3 is axiallyarranged with regard to the electrodes 21-26 with the configuration ofthe electrodes 20-26 defining a treatment or reaction zone whichcoincides approximately with the inter-electrode space. As will beappreciated by those skilled in the art, the electrodes 20-26, andparticularly the electrodes 21-26, may be arranged in any desiredconfiguration or arrangement to define or establish any desiredinter-electrode space (or any treatment/reaction zone) betweenthemselves or between themselves and the electrode 20. Nominally, in theimplantation discussed herein, the electrode 20 may be referred to as acathode while the electrodes 21-26 may function as anodes or,selectively as cathodes, as described below. Indeed, in someimplentations of the present invention each electrode may function,selectively, as anode or cathode. Further, while six electrodes 21-26are shown, any number of electrodes similarly constructed andelectrically connected may be provided in accordance with the desiredapplication. Those electrodes connected to function selectively as anodeor cathode are sometimes referred to herein as variable polarityelectrodes.

In operation, the switch 30 associated with electrode structure 20 iscontrolled, via its associated terminal(s) 31 and Switch Control 29, toconnect the negative terminal of Base Current Source 27 to the electrodestructure 20. Concurrently, one or more of the switches 30 associatedwith electrode structures 21-26 (and typically all of the electrodestructures 21-26) are selectively controlled, via their associatedcontrol terminal(s) 31 and Switch Control 29, to connect the positiveterminal of Base Current Source 29 to the selected ones of the electrodestructures 21-26. The output of Base Current Source 29 is selected andcontrolled, in known manner, to establish a base current and therebypreionize the inter-electrode space. Of course, it is within the scopeof the present invention to condition the inter-electrode space bypreionizing in any known manner. This conditioning (by preionizing, forexample) permits electrical discharges between selected electrodestructures with practical potential differences. Such discharges areprovided by selective application of pulses from Pulse Current Source 28across the electrode structures 20-26 in a manner described more fullybelow. As will be apparent to those familiar with the art, sequentialdischarges between electrodes 20-26 will "condition" the inter-electrodespace by maintaining an ionization level and may permit the base currentto be discontinued during continued operation.

Any of the electrode structures 20-26 may function as a cathode withregard to the electrical discharges. Thus, it is apparent that selectivecontrol of the switches 30 allows the control of electrical dischargessuch that those discharges extend throughout the inter-electrode space.This is described with reference to FIG. 5. As described above, theinteraction of these discharges with particulate matter to be treatedwithin the treatment zone and, in particular, the effects of microfieldswithin that zone, result in interaction with plasma (plasma action)without the necessity to establish and maintain an expanded plasma inthe manner of the prior art.

FIG. 3 illustrates a preferred control circuit, and in particular, apreferred implementation of the switches 30 of FIG. 2. Throughout theseveral figures, like reference numerals are used to designate likeelements. In the illustrated embodiment, the switches 30 are formed byone or more gate turn-off thyristors (GTO). It is to be understood,however, that other semiconducting power switches may be employed toimplement the present invention, including bipolar junction transistors,MOSFET technology and other thyristors to provide current pulses. In theembodiment of FIG. 3, suitable switching control circuitry (representedat 29) is connected to the GTO control electrode, as described above,and as illustrated in FIG. 4 with respect to switch 30, in known manner.In the discussion of the present invention, the various thyristors aredescribed as being "on" (conducting) or "off" (nonconducting) withcontrol circuitry 29 applying appropriate control signals to the controlelectrode of the GTO to achieve that state. The switch 30 associatedwith each of the electrodes 20-26 is formed of three GTO's labeled "C"(for cathode), "P" (for pulse), and "B" (for base current). The positiveoutput of the pulse current source 28 is connected to each of the GTO'slabeled "P" while the positive output of base current source 27 isconnected to each of the GTO's labeled "B" via magnetically linkedinductors 32 which enhance current sharing, as will be understood bythose skilled in the art.

In operation, and assuming a "conical" electrode configuration such asthat shown in FIG. 2, the switch 30 associated with electrode 20 iscontrolled such that electrode 20 functions as a cathode. That is, the"C" GTO associated with electrode 20 is conducting and the associated"B" and "P" GTO are "off". The "C" GTO's associated with electrodes21-26 are "off." Each of the "B" GTO's associated with electrodes 21-26may be conducting such that current will flow between the "cathode"electrode 20 on one hand, and the "anode" electrodes 21-26 on the other.This current is selected to preionize the inter-electrode space andestablish the conditions necessary for an arc discharge between theelectrode 20 and the electrodes 21-26 at a practical potentialdifference. As noted above, preionization may, alternatively or inaddition, be accomplished in any convenient manner.

With proper conditioning of the inter-electrode space (preionizationestablished via Base Current Source 27 as described above, for example)an output from Pulse Current Source 28 will be applied to each of the"P" GTO's associated with electrodes 21-26. Under the control of SwitchControl 29, one of the GTO's may be rendered "on" resulting in an arcdischarge between its associated electrode 21-26 and the cathodeelectrode 20. It is apparent, that Switch Control 29 may be employed toestablish a desired sequence of pulses (between the electrodes 21-26 andelectrode 20) as will be described more fully below.

Terminals 35 are illustrated in FIGS. 3 and 4 in association with eachof the electrodes 20-26. The terminals 35 may be employed in conjunctionwith a Current Detector 36 to detect the relative current between eachor any of the electrodes 20-26 which are functioning as anode. Suchcurrent and associated voltage are representative of the loading of thefeedstock being treated in the proximity to the relevant electrode. Thisinformation can be utilized for selection of firing order or otherappropriate action which may depend on the relative loading conditionswithin the area or field of influence of a particular electrode. Theconnection between terminal 35 associated with each of the electrodes20-26 is represented by the terminal 35 associated with Current Detector36. The specific connections are not illustrated in FIG. 3 for the sakeof clarity.

Referring now to FIG. 4, there is shown a modification to portions ofthe embodiment illustrated in FIG. 3 and, in particular, modificationsto the switches 30 associated with each of the electrodes 20-26. Asshown in FIG. 4, "C" GTO 40 corresponds to the "C" GTO of the switches30 of FIG. 3 while "B" and "P" GTO's 41 and 42 correspond to the "B" and"P" GTO's, respectively. The terminals 43 and 44 may be connected to thenegative and positive outputs of a Base Current Source such as thatshown at 27 in FIG. 3, with the terminal 43 also being connected to thenegative output of a Pulse Current Source such as that shown at 28 inFIG. 3. The terminal 45 in FIG. 4 may be connected to the positiveoutput of a Pulse Current Source such as that shown at 28 in FIG. 3. Theelectrode 46 may represent any of the electrode structures 20-26 in FIG.3.

To this point, the elements described in FIG. 4 correspond directly tothose illustrated in FIG. 3 as does the connection of Current Detector36 via terminal 35 and the control of the GTO's via Switch Control 29.In the modification of FIG. 4, the terminal 50 is adapted for connectionto the negative output of an additional Pulse Current Source which maycorrespond in kind to that illustrated at 28 in FIG. 3, while theterminal 51 is adapted for connection to the positive output of thatPulse Current Source. The terminal 50 may also be connected to thenegative output of a Base Current Source similar in kind to thatillustrated at 27 in FIG. 3, while the negative output of that secondBase Current Source is connected to the cathode electrode 20 in a mannerwhich will be apparent to those familiar with the art. A second "C" GTO52 is provided at terminal 50 while an additional "P" GTO 53 is providedat terminal 51. The GTO's 52 and 53 correspond in function to the GTO's40 and 41 but are connected to second or additional Pulse CurrentSources and Base Current Sources to provide a second set of pulseseither as a supplement to the first set of pulses, as by beingsuperimposed with them, or as a set of independent pulses.

Referring now to FIGS. 5A-5F, there is diagrammatically illustrated aseries of circularly arranged electrodes corresponding to thearrangement of electrode structures 21-26 of FIG. 2. In FIGS. 5A-5F,dashed lines extending between the electrode structures 21-26 representdiscrete electrical discharges established by the control systemsdescribed above, and particularly the control system of FIG. 3. Assuminga properly conditioned (preionized) inter-electrode space, each, andany, of the electrodes 21-26 may be selected to function as a cathodewith others selectively functioning as anodes. For example, in FIG. 5Aelectrode structure 23 is functioning as a cathode while electrodestructures 21, 26, and 25 are sequentially functioning as anodes. Thatis, discrete electrical discharge is first established (via PulseCurrent Source 28) between electrode (cathode) 23 and electrodes (anode)21. The next pulse from Pulse Current Source 28, is applied betweenelectrode 23 as cathode and electrode 26 as anode under the control ofswitch control 29. Similarly, the next pulse is applied between theelectrode 23 as cathode and electrode 25 as anode. Thereafter, theswitch control 29 may be operative to select electrode structure 22 ascathode and electrode structures 24- 26 as anodes with a series ofdiscrete electrical discharges cycling between those electrodes asrepresented in FIG. 5B. Essentially, the sequential firing representedin each of the FIGS. 5A-5F do not exist at the same time although theremay be some overlap. Further, by selectively switching the cathode andanode electrodes through the sequence selected by FIGS. 5A-5F the entirevolume of the inter-electrode space is subjected to an electricaldischarge. Thus, particles within that volume are subjected to atreatment in accordance with the present invention. Of course, anyfiring sequence may be employed including multiple discharges generatedby multiple pulse and base current sources as described above withreference to FIG. 4. Further, the electrode 20 may be employed (ascathode or anode) within a reactor in accordance with the presentinvention, while the inter-electrode space may be modified by movementof one or more of electrodes. Indeed, electrode configuration can beeasily changed to any desired configuration dependent upon theparticular application and the requirements of that application. Theelectrode configuration and firing sequence and timing are selected suchthat substantially the entire inter-electrode space is subjected todiscrete electrical discharges within a time interval less, andpreferably considerably less, than the expected residence time ofparticles to be treated within the inter-electrode space. This may beaccomplished by a selected sequence of discrete electrical discharges ina time interval less, and preferably considerably less, than the transittime of particulate matter to be treated through the reaction zone ofthe inter-electrode space.

The table of FIG. 6 represents the conduction/nonconduction (on=X,off=O) for the firing sequence represented in FIG. 5A. In the table, thefirst row indicates the particular electrode structure, while row twoindicates the particular "C", "B", and "P" GTO's associated with eachelectrode. Rows 3-5 of the table represent the first, second, and thirdpulses delivered by Pulse Current Source 28. An inspection of the tableshows that the "C" GTO associated with the electrode 23 is on throughoutthe three pulses while the "C" GTO associated with the other electrodesis off. The "P" GTO associated with electrode 23 is off, while the "B"GTO associated with the other electrodes are on. This provides a basecurrent via Base Current Source 27 between the cathode of electrode 23and the other electrodes which serve as anodes. Concurrently with thefirst pulse from Current Pulse Source 28, the "P" GTO associated withelectrode 21 is conducting (on) thereby applying a potential between theelectrode structures 21 and 23 resulting in a discrete electricaldischarge as represented by the dash line between those electrodestructures in FIG. 5A. A second pulse from Current Pulse Source 28 findsthe "P" GTO associated with electrode structure 21 off, while the "P"GTO associated with electrode structure 26 on. Thus, a discharge isapplied between electrode structures 23 and 26 as represented by thedashed line between those electrode structures in FIG. 5A. The bottomline shows the state of the GTO's during the third pulse in the sequenceresulting in an electrical discharge between the cathode of electrodestructure 23 and the anode 25. Thereafter, any of the electrodestructures 21-26 may be employed as a cathode with its associated "C"GTO turned on and its associated "P" GTO turned off. The "C" and "B"GTO's of the other electrode structures are in the opposite conditionwhile the "P" GTO of the electrode it is desired to function as an anodeis turned on concurrently with a pulse from the Current Pulse Source 28.Electrode structure 20 is capable, in the illustrated implentation, offunctioning as cathode or anode dependent on the state of its associate"C", "B" and "P" GTO's.

It is apparent from this description that each of the electrodestructures 20-26 can function alternatively as cathode or anode therebyexhibiting a variable polarity. Further, the discharges may follow anydesired sequence utilizing one of the electrodes as cathode while theselection of electrodes as cathode can similarly may follow any desiredsequence. As noted above, the electrodes may be positioned in anydesired configuration and may be moveable, in known manner, to modifythat configuration during operation or initial set-up. For example, theelectrode configuration described above establishes an essentiallyconical inter-electrode space when the central cathode 20 is considered.Other, non-conical, configurations are contemplated by the presentinvention. Also, it has been observed that resonance phenomena,naturally occurring or induced, interacting with the entrained particlesimprove their treatment. In addition, treatment zones may be "stacked"(multiple treatment zones positioned sequentially in the particle path)with different zones having the same or different electrodeconfigurations. In order to smooth the operation of a reactor inaccordance with the present invention, a magnetic field coil, with anadjustable power supply may be provided in a manner known to thoseskilled in the art. Finally, particulate matter to be treated, and gasesfor plasma formation and/or stabilization, may be introduced into thereaction zone in any known manner, in accordance with the teachings ofthe incorporated patent, for example. It is therefore to be understood,that any configuration of electrodes consistent with the treatment ofparticulate matter by plasma action through the utilization of discreteelectrical discharges is within the scope of the present invention asdescribed in the appended claims.

What is claimed is:
 1. A method of treating particulate matter byelectrical discharge comprising the steps of:positioning a plurality ofelectrode structures to define a desired inter-electrode space;preionizing the inter-electrode space; passing particulate matter to betreated through the inter-electrode space; and subjecting substantiallythe entire inter-electrode space to discrete electrical dischargeswithin a time interval considerably less than the expected residencetime of a particle to be treated within the inter-electrode space. 2.The method of claim 1, further comprising the step of establishing abase current between at least some of said electrode structures.